You want pork shoulder aka pork butt aka boston butt. I make an indoor version from Cooks Illustrated that is pretty good (not as good as from a smoker, though). I brine it, then do a rub before roasting.

A shoulder or a butt (same cut, different names in different markets), bone in. Yes, season first, a dry rub would be better than a marinade, since this cut tends to be on the large size. The put into the slow cooker with just enough broth to get it going. The meat will give up a lot of juice as it cooks. When you've got it shredded, mix in the BBQ sauce of choice.

the wonderful thing about thsi cut of meat is that you don't have to do very much to make it terrific. I usually just throw a 3-7 lb butt in a slow cooker and let it go overnight. You can add a dry rub, but if you are going to season it afterwards (NC or Texas style) then there is really no need.

Some other variations include Hawaiian, with a little Kalua or with a chili-rub.

I don't care for brining pork that is to be used as pulled pork to much. But, i do a rub followed by a nice sear and then slow cook it with a little water to start and I try to remove it whole- pick out the whole peices of meat to seperate from fat. Then I shred with two forks and add it back to the juices from cooking and on a high heat burner cook the shredded meat until all juices are absorbed. If you like a BBQ sauced style add some BBQ Sauce to the cooking liquid before adding meat back in. In a smoker though I do it a totally different way.

My never-fail recipe -- and I agree with everyone on the butt/shoulder selection -- is to rub down in a dry rub or a paste that's based on onion and garlic (typical in Caribbean preparations), then wrap tightly in plastic and refrigerate overnight. Sear it on all sides in a heavy pot, and if you're going to cook in the same pot, add just a little liquid (beer works well, or orange juice if you're going to go the Caribbean route; just pick something that seems to match well with your rub), clap on the top and braise that baby at about 250 for an hour per pound. If you're going the slow-cooker route, just move it over there after you sear it; no additional liquid needed unless you want it for seasoning purposes.